Gary Cote wrote:

>I'm not aware of much in the way of guidelines that will help you out here.
>
>rfc3261 says the UAS may send as many provisional responses as it likes,
>that proxies must immediately forward all non-100 provisional responses
>(unless they've already forwarded a final response), and that, if the session
>takes a while to set up, the UAS should send a non-100 provisional response
>at least every minute.
>  
>

Thanks. Thats the answer I was looking for. I see that in RFC 3261 
section 13.3.1.1  it says:

   To prevent cancellation, the UAS MUST send a non-100
   provisional response at every minute, to handle the possibility of
   lost provisional responses.


I think it implies you should send Ringing every minute (not exponential 
backoff).


>If you're sending multiple ringing responses for purposes of redundant
>signaling,
>then you might consider some exponential backoff algorithm using T1 (or some
>multiple of T1) as a starting interval. But, then, you might want to
>consider using
>100rel instead.
>
>Just some ideas ... take 'em or leave 'em. Good luck, regardless.
>
>  
>


-- 
M. Ranganathan 

Advanced Networking Technologies Division,
National Institute of Standards and Technology (NIST),
100 Bureau Drive, Stop 8920, Gaithersburg, MD 20899. 
Advanced Networking Technologies For the People!  


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